System and method for determining audio characteristics from within a body

ABSTRACT

A system for simultaneously detecting audio-characteristics within a body over multiple body surface locations comprising a coherent light source directing at least one coherent light beam toward the body surface locations, an imager acquiring a plurality of defocused images, each is of reflections of the coherent light beam from the body surface locations. Each image includes at least one speckle pattern, each corresponding to a respective coherent light beam and further associated with a time-tag. A processor, coupled with the imager, determines in-image displacements over time of each of a plurality of regional speckle patterns according to said acquired images. Each one of the regional speckle patterns is at least a portion of a respective speckle pattern. Each regional speckle pattern is associated with a respective different body surface location. The processor determines the audio-characteristics according to the in-image displacements over time of the regional speckle patterns.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/578,618, filed Nov. 30, 2017, which is the U.S. National PhaseApplication under 35 U.S.C. § 371 of International Application No.PCT/IL2016/050559, filed May 30, 2016, designating the U.S. andpublished as WO 2016/193970 A1 on Dec. 8, 2016 which claims the benefitof Israel Patent Application No. 239113, filed Jun. 1, 2015, all ofwhich are hereby incorporated by reference in their entireties.

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to speckle metrology in general, and tosystems and methods for simultaneously determining audio characteristicsfrom within a body over multiple body surface locations, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Detecting sound by employing laser speckle interferometry is known inthe art. To that end a laser beam is projected toward the sound sourceor on to a surface acoustically coupled with the sound source (i.e., asurface which vibrates according to the sound produced by the soundsource). The laser beam impinges on the surface and diffusively reflectstherefrom. The diffusive reflection of different portions of the lightbeam results in a random shift of the phases of the portions of thecorresponding light waves and a random distribution of the intensitiesthereof. Consequently, the waves corresponding to the diffusivelyreflected portions of the beam interfere with each other. This resultsin a light distribution with varying intensity. These random variationsin the intensity create a speckle pattern for each light beam. Thespeckle pattern varies with the vibrations of the surface. An imageracquires an image of the reflection of the laser beam from the surface.These images of the reflection of the laser beam include specklepatterns. The shift of the speckle patterns between subsequent images isrelated to the vibrations of the surface and thus to the sound producedby the sound source.

Reference is now made to FIG. 1 , which is a schematic illustration of asystem, generally referenced 10, for determining the vibrations of anobject, which is known in the art. System 10 includes an imager 12.Imager 12 includes an imaging sensor 14 and a lens 16. Lens 16 isoptically coupled with imaging sensor 14. A beam of coherent light 18(e.g., a laser light) impinges on the surface of an object 20 anddiffusively reflects therefrom. As mentioned above, this diffusivereflection results in a speckle pattern. Imager 12 acquires the specklepatterns in a defocused image plane 22. This defocused image plane islocated at a distance Z from the object. The angular displacement of theobject results in a shift, ΔH, of the speckle pattern in defocused imageplane 22 and thus of the speckle pattern in the acquired image.

The publication to Zalevsky et al. entitled “Simultaneous RemoteExtraction of Multiple Speech Sources and Heart Beats from SecondarySpeckles Pattern” directs to a system for extraction of remote sounds.In the system directed to by Zalevsky, a laser beam is directed towardan object and employs a defocused image and detects temporal intensityfluctuations of the imaged speckles pattern and their trajectory. Fromthe trajectories of the speckles pattern the system directed to byZalevsky detects speech sounds and heartbeat sounds.

U.S. Pat. No. 8,286,493 to Bakish, entitled “Sound Source Separation andMonitoring Using Direction Coherent Electromagnetic Waves” directs to asystem and methods in which a plurality of laser beams are pointedtoward multiple sound sources. The reflection of each of the beams isrelated to a corresponding sound source. The speckle pattern resultingfrom the reflection of each beam is analyzed to determine the soundproduced by the corresponding source. Thus, source separation may beachieved.

The publication to Chen et al., entitled “Audio Signal ReconstructionsBased on Adaptively Selected Seed Points from Laser Speckle Images”directs to a method for estimating the vibrations of an object accordingto variations in the gray level values of selected pixels, also referredto as seed points, in a defocused image of the speckle pattern. To thatend, the method directed to Chen acquires a plurality of images anddetermines a linear correspondence between the variations in the graylevel values of the seed points and the vibration of the object byestimating the parameters that minimize the difference between thevibration of the object at two different seed points, across all images(i.e., since the difference between the equations are used the vibrationis not a parameter in the optimization). The vibration between images isdetermined as the weighted sum of the vibration due to each seed point.

The publication entitled “Breath Sound Distribution of Patient WithPneumonia and Pleural Effusion” to Mor et al., describes theexperimental results of a system for detecting a breath sounddistribution map. The system directed to by Mor includes 40 contactsound sensors, assembled on two planar arrays, which cover the posteriorlung area. The sensors are attached to the patient's back by low-suctionvacuum controlled by a computer. The sounds captured by the sensors arefiltered to the desired frequency range of breath (between 150-250Hertz). The signals are processed and the breath sound distribution isdisplayed as a grayscale image. Areas with high lung vibration energyappear black and areas with low lung vibration energy appear light grey.A physician identifies whether the patient is suffering from Pneumoniaor Pleural Effusion based on these images.

PCT Application Publication 2002/036015 to Tearney et al directs toemploying focused images of laser speckles for measuring microscopicmotion (e.g., resulting from blood flow), such as Brownian motion oftissue in vivo, to gather information about the tissue. According to D1,coherent or partially coherent light is reflected from the tissue toform a speckle pattern at a detector. Due to motion of reflectors withinthe tissue, the speckle pattern changes over time. In operation,coherent light, such as laser light is transmitted through optical fibertoward a tissue sample (e.g., static tissue, moving tissue,atherosclerotic plaque and the like). The device can be placed directlyin contact with the sample or a short distance therefrom. The lightenters the sample, where it is reflected by molecules, cellular debrisor microstructures (such as organelles, microtubules), proteins,cholesterol crystals. The light remitted from the sample is focused onthe distal end of a fibers array (fibroscope). The focused light travelsthrough the fibers to a CCD detector. Due to interference, a specklepattern forms at the CCD detector. The resulting speckle pattern isanalyzed. According to Tearney, a reference image is acquired andcorrelated with successive images. Since the speckle pattern is eachsuccessive image is different the correlation between the acquired imageand the reference image decreases. According to Tearney, variousphysiological conditions can be determined from the de-correlation timeconstant. It is noted that Tearney does not measure the motion thatcause the change in the speckle pattern just the result of such amotion. Furthermore, Tearney directs to illuminating multiple locationsof the tissue in succession, forming a separate series of specklepatterns for each respective location, and then analyzing each separateseries of speckle patterns and comparing the separate series to deducestructural and/or biomechanical differences between the respectivelocations of the tissue.

SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method andsystem for simultaneously detecting audio characteristics from within abody, over multiple body surface locations.

In accordance with the disclosed technique, there is thus provided asystem for simultaneously detecting audio characteristics from within abody, over multiple body surface locations. The system includes acoherent light source, an imager and a processor. The processor iscoupled with the imager. The coherent light source directs at least onecoherent light beam toward the body surface locations. The at least onecoherent light beam impinges on the body surface locations. The imageracquires a plurality of defocused images, each image is of reflectionsof the at least one coherent light beam from the body surface locations.Each image includes at least one speckle pattern, each speckle patterncorresponds to a respective one of the at least one coherent light beam.Each image is further associated with a time-tag. The processordetermines in-image displacements over time of each of a plurality ofregional speckle patterns according to the acquired images. Each one ofthe regional speckle patterns is at least a portion of a respective oneof the at least one speckle pattern. Each one of the regional specklepatterns is associated with a respective different one of the bodysurface locations. The processor determines the audio characteristicsaccording to the in-image displacements over time of the regionalspeckle patterns.

In accordance with another aspect of the disclosed technique, there isthus provided method for simultaneously detecting audio characteristicswithin a body, over multiple body surface locations. The method includesthe procedures of directing at least one coherent light beam toward thebody surface locations, acquiring a plurality of defocused images of thebody surface locations, determining the in-image displacement over timein each of a plurality of regional speckle patterns according to theacquired images and determining the audio characteristics originatingfrom within the body at each of the body surface locations according tothe in-image displacement over time in the respective regional specklepattern. The at least one coherent light beam impinges on the bodysurface locations. Each image is of reflections of the at least onecoherent light beam from the body surface locations. Each image includesat least one speckle pattern, each corresponds to a respective one ofthe at least one coherent light beam. Each image is associated with atime-tag. Each one of the regional speckle patterns is at least aportion of a respective one of the at least one speckle pattern. Eachone of the regional speckle patterns is associated with a respectivedifferent one of the body surface locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fullyfrom the following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a schematic illustration of a system for determining thevibrations of an object, which is known in the art;

FIG. 2 is a schematic illustration of a system for simultaneouslydetecting audio characteristics within a body, over multiple bodysurface locations, constructed and operative in accordance with anembodiment of the disclosed technique;

FIG. 3 is a schematic illustration of a system for simultaneouslydetecting audio characteristics within a body, over multiple bodysurface locations, constructed and operative in accordance with anotherembodiment of the disclosed technique;

FIGS. 4A and 4B are schematic illustration of an exemplary userinterface constructed and operative in accordance with a furtherembodiment of the disclosed technique;

FIG. 5 is a schematic illustration of a method for simultaneouslydetecting audio characteristics within a body, over multiple bodysurface locations, operative in accordance with another embodiment ofthe disclosed technique; and

FIGS. 6A-6D are schematic illustrations of an example for simultaneouslydetecting audio characteristics within a body, over multiple bodysurface locations, in accordance with another embodiment of thedisclosed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art byproviding a system and a method for simultaneous detection of audiocharacteristics within a body, over multiple body surface locations. Theterm “audio characteristics” relate herein to an audio signal of a soundproduced from within the body or to the characteristics of that sound(e.g., spectrum, spectrogram, sound pressure level, sound power, timedelay between signals measured on different body surface locations,energy and the like). The sound from within the body may be produced,for example, by an organ (e.g., the heart, the lungs, the stomach or theintestines). The sound from within the body may also be that produced byan embryo (e.g., by the heart of the embryo or by the motion of theembryo within the womb). The system according to the disclosed techniqueincludes a coherent light source, which directs at least one coherentlight beam toward body surface locations and an imager, which acquires aplurality of defocused images of the reflections of the at least onecoherent light beam from the body surface locations. Each image includesat least one speckle pattern corresponding to a respective coherentlight beam. Each image is further associated with a time-tag. Aprocessor, coupled with the imager, determines in-image displacementover time of each of a plurality of regional speckle patterns accordingto the acquired images. Each one of the regional speckle patterns beingat least a portion of a respective speckle pattern associated therewith(e.g., two regional speckle patterns may be a portion of a singlespeckle pattern). Each of the regional speckle patterns is associatedwith a respective different one of the body surface locations. In otherwords, each of at least a portion of a speckle pattern may be associatedwith a different body surface location and define a regional specklepattern. The processor determines the audio characteristics originatingfrom within the body at each of the body surface location, according tothe in-image displacement over time of the respective regional specklepattern. The processor compares the determined audio characteristicswith stored audio characteristics corresponding to known physiologicalconditions, thereby attempting to detect at least one physiologicalcondition. A graphical representation of these audio characteristics maybe displayed on a display. A motion compensator compensates for theeffects of relative motion between the patient and the imager, on thedetermined audio characteristics. An audio reproduction sub-system mayreproduce the sounds from within the body according to the determinedsound signal. Also, a user may select the locations of interestcorresponding to the regional speckle patterns with the aid of a userinterface (UI).

Reference is now made to FIG. 2 , which is a schematic illustration of asystem, generally referenced 100, for simultaneously detecting audiocharacteristics within a body, over multiple body surface locations,constructed and operative in accordance with an embodiment of thedisclosed technique. System 100 includes a coherent light source 102, animager 104, a processor 106, a memory 108, a display 110 and an audioreproduction sub-system 112. Processor 106 includes a motion compensator114. Processor 106 is coupled with imager 104, memory 108, display 110and with audio reproduction sub-system 112. Processor 106 is optionallycoupled with coherent light source 102 (i.e., as indicated by thehatched line in FIG. 1 ).

Coherent light source 102 emits a beam or beams of monochromaticcoherent light. Coherent light source 102 is, for example, a laser lightsource. Imager 104 includes an imager sensor array (not shown) such as aCharged Coupled Device (CCD) sensor array or Complementary Metal OxideSemiconductor (CMOS) sensor array sensitive at the wavelength of thelight emitted by coherent light source 102.

Coherent light source 102 emits a plurality of light beams, such aslight beam 116, each toward a respective one of a plurality of bodysurface locations 118 ₁, 118 ₂, 118 ₃, 118 ₄, 118 ₅ and 118 ₆ of patient120. Each of the plurality of light beams impinges on the respective oneof body surface locations 118 ₁, 118 ₂, 118 ₃, 118 ₄, 118 ₅ and 118 ₆,and diffusively reflects therefrom (i.e., each ray is reflected at arandom direction) which, as mentioned above, results in a specklepattern across each light beam.

Imager 104 acquires a plurality of defocused images, such as image 122,of reflections of the light beams from body surface locations 118 ₁-118₆. Each image including a plurality of speckle patterns such as specklepattern 124. Each one of the speckle patterns corresponds to arespective light beam reflected from body surface locations 118 ₁-118 ₆.Thus, each of the speckle patterns correspond to a respective bodysurface location 118 ₁-118 ₆. Imager 104 further associates each imagewith a respective time-tag. Imager 104 provides the images acquiredthereby to processor 106.

Processor 106 determines the in-image displacement over time in each ofa plurality of regional speckle patterns 126 ₁, 126 ₂, 126 ₃, 126 ₄, 126₅ and 126 ₆ according to the acquired images. Each one of the regionalspeckle patterns 126 ₁-126 ₆ is associated with a respective differentone of the body surface locations 118 ₁-118 ₆. In the example set forthin FIG. 2 , each regional speckle patterns 126 ₁-126 ₆ is alsoassociated with a different respective speckle pattern (i.e., no tworegional speckle patterns are associated with the same respectivespeckle patter). In the defocused images, the vibrations and motion ofthe body surface locations 118 ₁-118 ₆ result in an in-imagedisplacement of the corresponding regional speckle patterns 126 ₁, 126₂, 126 ₃, 126 ₄, 126 ₅ and 126 ₆ between two images. The term ‘in-imagedisplacement’ herein relates to the difference between the pixelcoordinates of the speckle pattern (e.g., of the center of mass of thespeckle pattern) in two different images. Processor 106 may determinethe in-image displacements over time in each of a plurality of regionalspeckle patterns 126 ₁-126 ₆. As further explained below, processor 106determines the vibrations of each one of body surface locations 118₁-118 ₆. These vibrations may be caused by sound produced from withinthe body. Thus, processor 106 determines the audio characteristics atbody surface locations 118 ₁-118 ₆, according to in-image displacementsover time in the respective regional speckle patterns 126 ₁-126 ₆. Asmentioned above, the vibrations of body surface locations 118 ₁-118 ₆,and thus the audio characteristics corresponding thereto, may be inducedfrom within body. It is also noted that at least some of body surfacelocations 118 ₁-118 ₆ may partially overlap with each other therebyincreasing the spatial resolution of the system.

Following is an example of determining the vibrations of each one ofbody surface locations 118 ₁-118 ₆, and thus of the audiocharacteristics thereof, according to the plurality of images of therespective regional speckle patterns 126 ₁-126 ₆. Processor 106cross-correlates each pair of successive selected ones of the acquiredimages (i.e., as determined according to the time-tag associated witheach image). Processor 106 determines the relative shift between eachsuccessive pair of images accordingly to the result of the respectivecross-correlations (e.g., according to the location of the maxima of theresult of the cross-correlation). Processor 106 determines the vibrationof body surface locations 118 ₁-118 ₆ according to the relative shiftbetween each successive pair of images. The angular displacement of thebody about a vertical axis 128 results in a corresponding horizontalshift of the regional speckle patterns 126 ₁, 126 ₂, 126 ₃, 126 ₄, 126 ₅and 126 ₆ in the defocused image plane. The angular displacement of thebody about a horizontal axis 130 results in a vertical shift of theregional speckle pattern 126 ₁, 126 ₂, 126 ₃, 126 ₄, 126 ₅ and 126 ₆ inthe defocused image plane. Thus, the angular displacement of the bodyabout the vertical axis 128 or horizontal axis 130 results in acorresponding shift of the regional speckle patterns 126 ₁, 126 ₂, 126₃, 126 ₄, 126 ₅ and 126 ₆ in the acquired image as well. Therelationship between the angular displacement of the body surfacelocation about a single axis and the corresponding shift of a specklepattern in a successive pair of acquired images is as follows:

$\begin{matrix}{\theta = \frac{2{ZM}}{\Delta\; h}} & (1)\end{matrix}$where θ is the angular displacement (i.e., either about the verticalaxis or the horizontal axis) of the body surface location, Z is thedistance between the body surface location and the defocused imageplane, M is the magnification of the optics of imager 104 and Δh is thecorresponding relative shift (i.e., either horizontal or vertical)between the speckle patterns in a pair of successive images (i.e., asdetermined by the cross-correlation between the images). Alternatively,Processor 106 determines the vibrations of each one of body surfacelocations 118 ₁-118 ₆, and thus of—the audio characteristics thereof,according to variation of selected seed points as described above.

During the acquisition of the images, either patient 120 or imager 104or both, may move. This relative motion between patient 120 and imager104, also referred to herein as ‘common motion’, results in anadditional shift in the regional speckle patterns (i.e., other than theshift caused by the vibration of body surface locations 118 ₁-118 ₆).Thus, the total shift of one of regional speckle patterns 126 ₁, 126 ₂,126 ₃, 126 ₄, 126 ₅ and 126 ₆ (i.e., both due to the vibration of thebody surface locations 118 ₁-118 ₆ and due to the common motion), in asingle image axis (i.e., either the x axis or the y axis of the image)and between two subsequent images is as follows:

$\begin{matrix}{{\begin{pmatrix}{{ds}_{1}(t)} \\{{ds}_{2}(t)} \\\vdots \\{{ds}_{N}(t)}\end{pmatrix} + {\begin{pmatrix}a_{1,1} & a_{1,2} & a_{1,3} & a_{1,4} & a_{1,5} & a_{1,6} \\a_{2,1} & a_{2,2} & a_{2,3} & a_{2,4} & a_{2,5} & a_{2,6} \\\vdots & \vdots & \vdots & \vdots & \vdots & \vdots \\a_{N,1} & a_{N,2} & a_{N,3} & a_{N,4} & a_{N,5} & a_{N,6}\end{pmatrix} \cdot \begin{pmatrix}{{dx}(t)} \\{{dy}(t)} \\{{dz}(t)} \\{{dYaw}(t)} \\{{dPitch}(t)} \\{{dRoll}(t)}\end{pmatrix}}} = \begin{pmatrix}{{dS}_{1}(t)} \\{{dS}_{2}(t)} \\\vdots \\{{dS}_{N}(t)}\end{pmatrix}} & (2)\end{matrix}$In Equation (2), N relates to the number of regional speckle patterns,ds_(i)(t) relates to the in-image displacement (i.e., occurring betweenthe acquisition of two subsequent images) of a regional speckle patterncorresponding to body surface location i only due to the vibrationthereof. dSi(t) relates to the in-image displacement (i.e., alsooccurring between the acquisition of two subsequent images) of theregional speckle pattern corresponding to body surface location i due toboth the vibration thereof and the common motion. Further in equation(2) a_(i,j) are common motion coefficients in a motion compensationmatrix. A respective motion compensation matrix is associated with eachregional speckle pattern. Also in Equation (2) dx(t), dy_(i)(t),dz_(i)(t) relate to the change in the relative position between patient120 and imager 104 (i.e., between the acquisition times of the twosubsequent images) in the x, y and z axes respectively and dYaw_(i)(t),dPitch_(i)(t) and dRoll_(i)(t) relate to the change in the relativeorientation between patient 120 and imager 104 (i.e., also between theacquisition times of two subsequent images) about the yaw, pitch androll axes respectively. In vector and matrix notation, equation 2 may beexpressed as follows:{right arrow over (s)}(t)+M{right arrow over (F)}(t)={right arrow over(S)}(t)  (3)M is referred to herein as the ‘motion compensation matrix’ where theentries thereof are a_(i,j) of equation (2), {right arrow over (s)}(t)is a vector where the entries thereof are ds_(i)(t) of equation (2),{right arrow over (S)}(t) is a vector where the entries thereof aredS_(i)(t) of equation (2) and {right arrow over (F)}(t), referred toherein as the ‘relative motion vector’ is a vector where the entriesthereof are dx(t), dy_(i)(t), dz_(i)(t), dYaw_(i)(t), dPitch_(i)(t) anddRoll_(i)(t). According to equation (3), the displacement of theregional speckle pattern corresponding to body surface locations 118₁-118 ₆, only due to the vibration of the body surface locations, may beexpressed as follows:{right arrow over (s)}(t)={right arrow over (S)}(t)−M{right arrow over(F)}(t)  (4)

To compensate for relative motion between patient 120 and imager 104,motion compensator 114 requires information relating to {right arrowover (S)}(t), {right arrow over (F)}(t) and M. {right arrow over (S)}(t)is determined from the acquired images by employing a cross-correlationbetween a pair of successive images, as mentioned above. M is determinedeither during a calibration process or analytically as further explainedbelow. Thus, only {right arrow over (F)}(t)) is unknown.

Assuming that the average in-image displacement of regional specklepattern 126 ₁, 126 ₂, 126 ₃, 126 ₄, 126 ₅ and 126 ₆ corresponding tobody surface locations 118 ₁-118 ₆, only due to the vibration thereof,is small relative to the in-image displacement due to the common motion,the in-image displacement due to the relative motion between patient 102and imager 104 may be estimated as follows:M{right arrow over (F)}(t)={right arrow over (S)}(t)  (5)Motion compensator 114 may estimate {right arrow over (F)}(t)) byemploying the least squares method as follows:{right arrow over (F)}(t)=[M ^(T) M]⁻¹ M ^(T) {right arrow over(S)}(t)  (7)Thus, processor 106 determines the shift of regional speckle patterns126 ₁, 126 ₂, 126 ₃, 126 ₄, 126 ₅ and 126 ₆ corresponding to bodysurface locations 118 ₁-118 ₆ only due to the vibration thereof byemploying results of equation (7) with equation (4). It is noted thatequation (7) may be incorporated in equation (4) resulting in a singleequation to be solved without estimating) {right arrow over (F)}(t) asfollows:{right arrow over (s)}(t)={right arrow over (S)}(t)−M[M ^(T) M]⁻¹ M ^(T){right arrow over (S)}(t)  (8)It is further noted that, if the motion compensation matrix and therelative motion vector are unknown, motion compensator 114 may estimateboth by employing singular value decomposition (SVD) on {right arrowover (S)}(t). It is also noted that the number of regional specklepatterns employed for estimating the in-image displacement due commonmotion relates to the number of motion parameters (i.e., X, Y, Z, Pitch,Yaw, Roll) to be estimated. Each regional speckle pattern may beemployed for estimating two motion parameters. For example, fordetermining the in-image displacement due to common motion in the X, Yand Z axes and about the Pitch, Yaw and Roll axes (i.e., six motionparameters), at least three regional speckle patterns should beemployed.

System 100 may be employed to detect various physiological conditionscharacterized by the respective audio characteristics thereof. Forexample, system may be employed to detect heart arrhythmia, asthma,apnea, pneumonia and the like. To that end, memory 108 stores aplurality of audio characteristics corresponding to various knownphysiological conditions (i.e., may include the audio characteristicscorresponding to normal physiological conditions). Processor 106compares the determined audio characteristics corresponding to eachselected one of body surface locations 118 ₁-118 ₆ of interest with thestored audio characteristics (i.e., associated with substantially thesame body surface locations) of known physiological conditions, todetermine a correspondence there between. Alternatively or additionally,processor 106 compares the determined audio characteristicscorresponding to each body surface locations of interest with the audiocharacteristics corresponding to other ones of selected body surfacelocations of interest.

Following is an example of attempting to detect physiological conditionsaccording to determined and stored sound characteristics. Initially,processor 106 filters signals of interest (e.g., sounds relating to theheart, sound relating to breathing and the like) from the detected soundsignals associated with selected ones of body surface locations 118₁-118 ₆. Such filtering may be done in the frequency domain or in thetime domain. For example, heart sounds exhibit a higher frequency thanbreathing sounds, breathing sounds may be detected after the occurrenceof a PQR cycle. For each signal on interest, processor 106 determines arespective spectrogram. Processor 106 then compares the spectrogram ofeach signal of interest with a reference spectrogram (e.g., associatedwith known physiological condition) associated with substantially thesame body surface location. For example, processor 106 compares theintensities of the spectrograms corresponding to the selected ones ofbody surface locations relative to the intensities of the referencespectrograms (i.e., also corresponding to the same selected body surfacelocations). As a further example, processor 106 may cross-correlate thedetermined spectrograms with the reference spectrograms orcross-correlate portions of the determined spectrograms with portions ofthe reference spectrograms. Alternatively or additionally, processor 106compares the spectrogram of each signal of interest with the spectrogramcorresponding to other ones of selected body surface locations (e.g.,comparing the spectrogram corresponding to the left lower lung with thespectrogram corresponding to the right lower lung). As described above,processor 106 may compare the intensities of these spectrograms orcross-correlate these spectrograms (i.e. or portions thereof). It isnoted that spectrograms are brought herein as an example only, the abovedescribed may be employed with any one determined audio characteristics.For example, processor 106 may compare a determined sound signal with astored sound signal by cross-correlating the two signals. Processor 106may determine a correlation matrix between the determined sound signalswhich is related to the variance between the detected sound signals.

As mentioned above, the audio characteristics corresponding to bodysurface locations 118 ₁-118 ₆ may be produced from within the body(e.g., by an organ such as the heart, the lungs, the intestines or by anembryo). When the audio characteristics include a signal representingthe sound produced from within the body, processor 106 may provide thatsound signal to audio reproduction sub-system 112. Audio reproductionsub-system 112 (e.g., speakers or earphones) re-produces the sound fromwithin the body for the user to hear. Audio reproduction sub-system 112may be a ‘three-dimensional (3D) audio’ reproduction sub-system asfurther explained below. Processor 106 may provide the determined audiocharacteristics to display 110 which presents graphical representationsof the audio characteristics to the user. For example, display 110 maypresent a graph of the sound signal or a graph of the spectrum of thesound signal or both. Alternatively or additionally, display 110displays an image of the speckle pattern or the region of interest ofthe body surface or of the inner body. Display 110 may be a part of auser interface, as further explained below in conjunction with FIGS. 4Aand 4B.

As mentioned above, in the example set forth in FIG. 1 , each regionalspeckle patterns 126 ₁-126 ₆ is also associated with a differentrespective speckle pattern. However, that is not generally the case, twoor more regional speckle patterns may be associated with a differentportion of the same speckle pattern produced by a single beam.Nevertheless, each regional speckle pattern is associated with arespective different body surface location. Also, six body surfacelocations (i.e., body surface locations 118 ₁-118 ₆) are brought hereinas an example only. Less or more body surface location may be employed(e.g., according to user selection) as further elaborated below inconjunction with FIGS. 4A and 4B.

System 100 described hereinabove in conjunction with FIG. 2 employs aplurality of coherent light beams each illuminating body surfacelocations. However, a single coherent light beam, which illuminates theentire body region of interest (e.g., the thorax, the abdomen) may beemployed. This body region of interest includes all the plurality ofbody surface locations of interest. Reference is now made to FIG. 3 ,which is a schematic illustration of a system, generally referenced 150,for simultaneously detecting audio characteristics within a body, overmultiple body surface locations, constructed and operative in accordancewith another embodiment of the disclosed technique. System 150 includesa coherent light source 152, an imager 154, a processor 156, a memory158, a display 160 and an audio reproduction sub-system 162. Processor156 includes a motion compensator 164. Processor 156 is coupled withimager 154, memory 158, display 160 and with audio reproductionsub-system 162. Processor 156 is optionally coupled with coherent lightsource 152 (i.e., as indicated by the hatched line in FIG. 3 ).

Similarly to coherent light source 102 (FIG. 2 ), coherent light source152 emits monochromatic light. Coherent light source 152 is, forexample, a laser light source. Similarly to imager 104 (FIG. 2 ), imager154 includes an imager sensor array (not shown) such as a ChargedCoupled Device (CCD) sensor array or Complementary Metal OxideSemiconductor (CMOS) sensor array sensitive at the frequency of thelight emitted by coherent light source 152.

Coherent light source 152 emits a light beam 166 toward plurality ofbody surface locations 168 ₁, 168 ₂, 168 ₃, 168 ₄, 168 ₅ and 168 ₆ ofpatient 170. Light beam 166 impinges on a body region of interest ofpatient 170 and diffusively reflects therefrom, which results in aspeckle pattern. As mentioned above, the speckle pattern varies with thevibrations of the respective one of body surface locations 168 ₁-168 ₆,which may be partially induced by sound produced from within the body.It is also noted that six body surface locations (i.e., body surfacelocations 168 ₁-168 ₆) are brought herein as an example only. Less ormore body surface locations may be employed.

Imager 154 acquires a plurality of defocused images, such as image 172,of a reflection of light beam 166 from body surface locations 168 ₁-168₆. Each image includes a speckle pattern such as speckle pattern 174corresponding to light beam 166 reflected form body surface locations168 ₁-168 ₆. Imager 154 further associates each image with a respectivetime-tag, and provides the images acquired thereby to processor 156.

Processor 156 determines in-image displacement of each of a plurality ofregional speckle patterns 176 ₁, 176 ₂, 176 ₃, 176 ₄, 176 ₅ and 176 ₆according to the acquired images. Each one of the regional specklepatterns 176 ₁-176 ₆ is associated with a respective different one ofthe body surface locations 168 ₁-168 ₆ and thus, with a differentportion of speckle pattern 174. Processor 156 determines the vibrationsof each one of body surface locations 168 ₁-168 ₆. These vibrations maybe caused by sound produced from within the body at the body surfacelocations 168 ₁-168 ₆. Thus, processor 156 determines the audiocharacteristics at body surface location 168 ₁-168 ₆ according toin-image displacement of the respective regional speckle patterns 176₁-176 ₆ similarly to as described above in conjunction with FIG. 1 andEquation 1. Alternatively, Processor 156 determines the vibrations ofeach one of body surface locations 168 ₁-168 ₆, and thus of the audiocharacteristics thereof, according to variation of selected seed pointsalso as described above. As mentioned above, the audio characteristicscorresponding to body surface locations 168 ₁-168 ₆ may be produced fromwithin the body. Furthermore, motion compensator 164 compensates for therelative motion between of patient 170 and imager 154 similar to asdescribed above in conjunction with FIG. 1 and equations 2-8. Alsosimilar to as described above in conjunction with FIG. 1 , at least someof body surface locations 168 ₁-168 ₆ may partially overlap with eachother thereby increasing the spatial resolution of the system.

Further similar to system 100 (FIG. 2 ), system 150 may be employed todetect various physiological conditions. To that end, memory 158 storesa plurality of audio characteristics corresponding to various knownphysiological conditions. Processor 156 then compares the determinedaudio characteristics corresponding to each selected one of body surfacelocations 168 ₁-168 ₆ with reference audio characteristics (e.g.,associated with known physiological condition) associated withsubstantially the same body surface location. Alternatively oradditionally, processor 156 compares the determined audiocharacteristics corresponding to each body surface locations of interestwith the audio characteristics corresponding to other ones of selectedbody surface locations of interest.

Similar to as described above in conjunction with FIG. 1 , when theaudio characteristics include a signal representing the sound producedfrom within the body, processor 156 may provide that sound signal toaudio reproduction sub-system 162, which re-produces the sound fromwithin the body for the user to hear. Audio reproduction sub-system 162may also be a 3D audio reproduction sub-system. Also similar to asdescribed above in conjunction with FIG. 1 , Processor 156 may providethe determined audio characteristics to display 160 which presentsgraphical representations of the audio characteristics to the user.Alternatively or additionally, display 160 displays an image of thespeckle pattern or the region of interest of the body surface or of theinner body. Display 156 may also be a part of a user interface.

In a system according to the disclosed technique (e.g., system 100 ofFIG. 2 or system 150 of FIG. 3 ), a user may select locations ofinterest with the aid of a user interface (UI). For example, when a userwants to listen to the sounds produced by an embryo, the user selectsbody surface locations located on the abdomen. As a further example,when a user may want to listen to the sounds produced by the left lung,the user selects body surface locations located on left thorax.Alternatively, the display displays a model of the inner body region ofinterest or of the embryo and the user selects the body surfacelocations with the aid of this model.

Reference is now made to FIGS. 4A and 4B which are schematicillustration of an exemplary user interface, generally referenced 200,constructed and operative in accordance with a further embodiment of thedisclosed technique. User interface 200 may be employed with either oneof system 100 or system 150 described hereinabove in conjunction withFIG. 2 and FIG. 3 respectively. As such user interface is coupled withthe respective one of processor 110 (FIG. 2 ) or processor 160 (FIG. 3). User interface 200 includes a display 202 and a user selection 204.In FIGS. 4A and 4B, display 202 displays a location representations 206₁, 206 ₂, 206 ₃, 206 ₄, 206 ₅ and 206 ₆, superimposed on a model of anorgan of interest 208 (e.g., the heart and the lungs in FIGS. 4A and4B). Each one of location representations 206 ₁-206 ₆ corresponds to arespective body surface location 210 ₁, 210 ₂, 210 ₃, 210 ₄, 210 ₅ and210 ₆ on the body of patient 210. A user selects the body surfacelocations 210 ₁-210 ₆ of interest according to the location of locationrepresentations 206 ₁-206 ₆ on display 202. The user may select the bodysurface locations 208 ₁-208 ₆ of interest by employing user selection204. In the example set forth in FIGS. 4A and 4B, user selection 204includes predefined options and a user defined option. Each of thepredefined options includes a different selection of body surfacelocations 210 ₁-210 ₆ suitable for a known situation. For example,option one depicted in FIG. 4A includes body surface locations suitablefor determining the audio characteristics corresponding to the heart andlungs of a male adult. Similarly, option two includes body surfacelocations suitable for determining the audio characteristicscorresponding to the heart and lungs of a female adult. Option threeincludes body surface locations suitable for determining the audiocharacteristics corresponding to the heart and lungs of a child (i.e.,the location representations 206 ₁-206 ₆ and the corresponding bodysurface locations 210 ₁-210 ₆ will be more densely distributed than bodysurface locations 210 ₁-210 ₆ of an adult).

With reference to FIG. 4B, when employing the user defined option inuser interface 200, the user may select the body surface locations 210₁-210 ₆ by moving location representations 206 ₁-206 ₆ (e.g., with theaid of a cursor) on display 202 to the desired location. In the exampleset forth in FIG. 4B, the user selects to determine the audiocharacteristics corresponding to the lungs only. When user interface 200is employed in conjunction with system 100 (FIG. 2 ), and the userselects body surface locations 210 ₁-210 ₆ by moving locationrepresentations 206 ₁-206 ₆, coherent light source 102 shall direct thelight beams emitted thereby toward selects body surface locations 210₁-210 ₆ according to the location of location representations 206 ₁-206₆ on display 202. Furthermore location representations 206 ₁-206 ₆ shallindicated the location of the regional speckle patterns 126 ₁-126 ₆ inthe images acquired by imager 104. When user interface 200 is employedin conjunction with system 150 (FIG. 3 ), and the user selects bodysurface locations 210 ₁-210 ₆ by moving location representations 206₁-206 ₆, coherent light source 152 shall directs the light beam emittedthereby toward body surface region of interest according to the locationof location representations 206 ₁-206 ₆ on display 202. Furthermorelocation representations 206 ₁-206 ₆ shall indicate the location of theregional speckle patterns 176 ₁-176 ₆ in the images acquired by imager154. For a user to be able to select body surface locations 210 ₁-210 ₆with the aid of user interface 200 and a model an organ of interest 208,the coordinate system associated with the model (herein ‘the modelcoordinate system’) and the coordinate system associated with the imageacquired by the imager should be registered with each other (e.g., withthe aid of fiducials) so the selection of location representations 206₁-206 ₆ shall corresponds to the body surface locations 210 ₁-210 ₆.Furthermore, the time delay between signals, originating from the samesource and measured at different body locations may be employed todetermine the exact position of the sound source. For example, each timedelay fits to a hyperbola in the model coordinate system supposing auniform propagation velocity. An intersection of at least two of suchhyperbolas defines a two dimensional location of the sound source. Alsocomparing between signals gathered at different defined positions thevarious internal body sounds (e.g., the sound of breathing) may becharacterized, for example, in terms of the above mentioned audiocharacteristics.

As mentioned above, audio reproduction sub-system 112 (FIG. 2 ) andaudio reproduction sub-system 162 (FIG. 3 ) may be a 3D audioreproduction sub-system. Such a 3D audio reproduction sub-systemreproduces the sound detected from within the body, which the user hearsas originating from the source of the sound (e.g., from the heart of thepatient). To that end, for example, the processor employs a Head RelatedTransfer Function (HRTF) to produce a binaural sound to be reproduced onheadphones. In general, for a 3D audio reproduction system to producethe sound, which the user hears as originating from the source of thesound, the spatial relationship between the source and the user shouldbe known (i.e., either fixed or tracked). For example, the user mayposition herself in front of the patient at a fixed relative positionduring examination. Alternatively, the spatial relationship between theuser and the source may be tracked by a tracking system (e.g., anoptical tracking system, an electromagnetic tracking system or anultrasound tracking system). The output of such a tracking system isused as the input for the HRTF.

Reference is now made to FIG. 5 , which is a schematic illustration of amethod for simultaneously detecting audio characteristics within a body,over multiple body surface locations, operative in accordance withanother embodiment of the disclosed technique. In procedure 250, atleast one coherent light beam is directed toward body surface locations.The at least one coherent light beam impinges on the body surfacelocations. With reference to FIG. 2 , coherent light source 102 directsa plurality of coherent light beams toward body surface locations 118₁-118 ₆. With reference to FIG. 3 , coherent light source 152 directscoherent light beams 266 toward body surface locations 168 ₁-168 ₆.

In procedure 252, a plurality of defocused images of the body surfacelocations are acquired. Each image is reflections of the at least onecoherent light beam from the body surface locations. Each one of theimages includes at least one speckle pattern, each speckle patterncorresponding to a respective one of the at least one coherent lightbeam. Each one of the images being further associated with a respectivetime-tag. With reference to FIG. 2 , imager 104 acquires a plurality ofdefocused images of body surface locations 118 ₁-118 ₆, each includingat least one speckle pattern corresponding to a respective coherentlight beam. With reference to FIG. 3 , imager 154 acquires a pluralityof defocused images of body surface locations 168 ₁-168 ₆, eachincluding at least one speckle pattern corresponding to a respectivecoherent light beam.

In procedure 254, the in-image displacement over time of each of aplurality of regional speckle patterns are determined according to theacquired images. Each regional speckle pattern is at least a portion ofa respective one of the at least one speckle pattern. Each regionalspeckle pattern is associated with a respective different one of thebody surface locations. With reference to FIG. 2 processor 106determines the in-image displacements over time of each of a pluralityof regional speckle patterns according to the acquired images. Withreference to FIG. 3 processor 156 determines the in-image displacementover time of each of a plurality of regional speckle patterns accordingto the acquired images.

In procedure 256, the effects of relative motion between the body andthe imager on the in-image displacements of the regional speckle patternare compensated. As mentioned above, the relative motion between thebody and the imager may result in an additional shift in the regionalspeckle patterns other than the shift caused by the vibration of thebody surface locations. The effect of the relative motion between thebody and the imager on the in-image displacements of the regionalspeckle pattern is compensated as described above in conjunction withequations 2-7. With reference to FIG. 2 , motion compensator 114,compensate the effect of the relative motion between the body of patient120 and the imager 102 on the in-image displacement of the regionalspeckle pattern 126 ₁-126 ₆. With reference to FIG. 3 , motioncompensator 164, compensates the effects of relative motion between thebody of patient 170 and the imager 152 on the in-image displacements ofthe regional speckle pattern 176 ₁-176 ₆. It is noted that when norelative motion exists between the body (e.g., when both the body andthe imager cannot move) there is no need to compensate the effects suchrelative motion.

In procedure 258, the audio characteristics originating from within thebody, at each of the body surface locations, are determined according tothe in-image displacements over time of the respective regional specklepattern. As mentioned above, sound originating from within the body mayresult in vibrations of the body surface. With reference to FIG. 2 ,processor 106 determines the audio characteristics originating fromwithin the body at each of the body surface locations according to thein-image displacements over time of the respective regional specklepattern. With reference to FIG. 3 , processor 156 determines the audiocharacteristics originating from within the body at each of the bodysurface locations according to the in-image displacements over time ofthe respective regional speckle pattern.

In procedure 260, the detection of at least one physiological conditionis attempted. A physiological condition may be detected by comparing thedetermined audio characteristics corresponding to each selected one ofbody surface locations with reference audio characteristicscorresponding to substantially the same body surface location.Alternatively or additionally, a physiological condition may be detectedby comparing the determined audio characteristics corresponding to eachbody surface locations of interest with the audio characteristicscorresponding to other ones of selected body surface locations ofinterest. With reference to FIG. 2 , memory 108 stores a plurality ofaudio characteristics corresponding to various known physiologicalconditions. Processor 106 compares the determined audio characteristicscorresponding to each selected one of body surface locations 118 ₁-118 ₆of interest with the stored audio characteristics corresponding to knownphysiological conditions, to determine a correspondence there between.Alternatively or additionally, processor 106 compares the determinedaudio characteristics corresponding to each body surface locations ofinterest with the audio characteristics corresponding to other ones ofselected body surface locations of interest. With reference to FIG. 3 ,memory 158 stores a plurality of audio characteristics corresponding tovarious known physiological conditions. Processor 106 then compares thedetermined audio characteristics corresponding to each selected one ofbody surface locations 168 ₁-168 ₆ with reference audio characteristicscorresponding to substantially the same body surface location.Alternatively or additionally, processor 156 compares the determinedaudio characteristics corresponding to each body surface locations ofinterest with the audio characteristics corresponding to other ones ofselected body surface locations of interest.

Reference is now made to FIGS. 6A-6D, which are schematic illustrationsof an example for simultaneously detecting audio characteristics withina body, over multiple body surface locations, in accordance with anotherembodiment of the disclosed. FIG. 6A depicts an acquired defocused image300 of a thorax of a patient 302 illuminated with a single beam ofcoherent light. Superimposed on image 300 are markings, ‘a’, ‘b’ and ‘c’of body surface locations from which audio characteristics are detected.Each of body surface locations ‘a’, ‘b’ and ‘c’ is associated with arespective regional speckle pattern (e.g., regional speckle patterns 176₁-176 ₆ in FIG. 3 ). With reference to FIGS. 6B-6D, FIG. 6B depicts theaudio characteristic 304 detected from body surface location ‘a’, FIG.6C depicts the audio characteristic 306 detected from body surfacelocation ‘b’, FIG. 6D depicts the audio characteristic 308 detected frombody surface location ‘c’. In FIGS. 6B-6D, detected audio characteristic304, 306 and 308 are sound signals from the heart of patient 302 wherethe horizontal axis is related to time and the vertical axis is relatedto amplitude.

It will be appreciated by persons skilled in the art that the disclosedtechnique is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the disclosed technique isdefined only by the claims, which follow.

The invention claimed is:
 1. A system for simultaneously detecting audiocharacteristics within a user's body, over multiple body surfacelocations, the system comprising: a coherent light source, directing atleast one coherent light beam toward and reflected from said bodysurface locations; an imager, configured to acquire a plurality ofdefocused images of said reflections, each image including at least onespeckle pattern, each speckle pattern corresponds to said at least onecoherent light beam, each image being associated with a time-tag; aprocessor, coupled with said imager, said processor determining in-imagedisplacements over time of each of a plurality of regional specklepatterns in said acquired images, each of said regional speckle patternsbeing at least a portion of said at least one speckle pattern, each oneof said regional speckle patterns corresponding to a different one ofsaid body surface locations, said processor determining said audiocharacteristics according to said in-image displacements over time ofsaid regional speckle patterns.
 2. The system according to claim 1,further including a memory and audio characteristics corresponding toknown physiological condition, said memory storing the audiocharacteristics corresponding to the known physiological condition. 3.The system according to claim 2, wherein said processor determineswhether said determined audio characteristics corresponds to at leastone known physiological condition by comparing said determined audiocharacteristics corresponding to each selected one of body surfacelocations of interest with said stored audio characteristicscorresponding to the known physiological condition.
 4. The systemaccording to claim 2, wherein said processor determines whether saiddetermined audio characteristics corresponds to at least one knownphysiological condition by comparing the audio characteristicscorresponding to each body surface locations of interest with the audiocharacteristics corresponding to other ones of selected body surfacelocations of interest.
 5. The system according to claim 1, furtherincludes an audio reproduction subsystem configured to reproduce soundscorresponding to said audio characteristics.
 6. The system according toclaim 5, wherein said audio reproduction subsystem is a three-dimensionaudio reproduction system configured to reproduce sound corresponding tosaid audio characteristics, which the user hears as originating from asource of the reproduced sound.
 7. The system according to claim 6,wherein said processor employs a Head Related Transfer Function toproduce a binaural sound to be reproduced on headphones.
 8. The systemaccording to claim 4, wherein said body surface locations correspond toregions of interest and where said region of interest is one of a thoraxand an abdomen.
 9. The system according to claim 1, wherein said audiocharacteristics are at least one of an audio signal; an audiospectrogram; spectrum; sound pressure level; sound power; time delaybetween signals measured on different body surface locations; andenergy.
 10. The system according to claim 1, wherein said processorfurther includes a motion compensator, said motion compensator isconfigured to compensate for effects on the in-image displacement ofeach respective regional speckle pattern corresponding to a relativemotion between said imager and each of said body surface locations. 11.The system according to claim 10, wherein said motion compensatorcompensates said effects according to the following:{right arrow over (s)}(t)={right arrow over (S)}(t)−M[M ^(T) M]⁻¹ M ^(T){right arrow over (S)}(t) wherein s(t) relates to the in-imagedisplacement of said regional speckle pattern corresponding to said bodysurface locations, wherein said body surface locations are vibrating,said in-image displacement is only due to the vibrations of said bodysurface locations, S(t) relates to the in-image displacement of theregional speckle pattern corresponding to said body surface locationsdue to both the relative motion between said imager and each of saidbody surface locations and the vibrations of said body surface locationsand M is a motion compensation matrix.
 12. The system according to claim1, further including a display for displaying at least one of: saidspeckle patterns; and a visual representation of said audiocharacteristics.
 13. The system according to claim, 12 further includinga user interface, said user interface including said display and a userselector, said selector allows selection of said body surface locationsaccording to one of predefined options and user defined locations. 14.The system according to claim 13, wherein, said body surface locationscorrespond to inner body locations and said body surface location areselected according to the inner body location for which said audiocharacteristics are to be determined.
 15. A method for simultaneouslydetecting audio characteristics within a user's body, over multiple bodysurface locations, the method comprising the procedures of: directing atleast one coherent light beam toward said body surface locations, saidat least one coherent light beam impinging on said body surfacelocations; acquiring a plurality of defocused images reflected saidcoherent light from said body surface, wherein each image includes atleast one speckle pattern corresponding to said at least one coherentlight beam, and each image being associated with a time-tag; determiningan in-image displacement over time in each of a plurality of regionalspeckle patterns, wherein each one of said regional speckle patternsbeing at least a portion of a respective one of said at least onespeckle pattern and each one of said regional speckle patterns beingassociated with a respective one of said body surface locations; anddetermining the audio characteristics originating from within the bodyat each of said body surface locations according to the in-imagedisplacement over time in respective regional speckle patterns.
 16. Themethod according to claim 15, further includes the step of attempting todetect at least one physiological condition.
 17. The method according toclaim 16, wherein said determined audio characteristics corresponding toeach selected one of body surface are compared with reference audiocharacteristics corresponding to substantially the same body surfacelocation thereby attempting to detect at least one physiologicalcondition.
 18. The method according to claim 16, wherein said determinedaudio characteristics corresponding to each body surface locations ofinterest are compared with the audio characteristics corresponding toother audio characteristics of other selected body surface locations ofinterest.
 19. The method according to claim 15, further including thestep of compensating effects of relative motion between the body andimager on the regional speckle pattern.
 20. The method according toclaim 19, wherein said effects of relative motion between the body andthe imager are compensated according to the following:{right arrow over (s)}(t)={right arrow over (S)}(t)−M[M ^(T) M]⁻¹ M ^(T){right arrow over (S)}(t) wherein s(t) relates to the in-imagedisplacement of said regional speckle pattern corresponding to said bodysurface locations where said body surface locations are vibrating, onlydue to the vibration of said body surface locations, S(t) relates to thein-image displacement of the regional speckle pattern corresponding tosaid body surface locations due to both the relative motion between saidimager and each of said body surface locations and the vibrations ofsaid body surface locations and M is a motion compensation matrix. 21.The method according to claim 15, wherein said body surface locationscorrespond to regions of interest and where said regions of interest areone of a thorax and an abdomen.
 22. The method according to claim 15,wherein said audio characteristics are at least one of: an audio signal;an audio spectrogram spectrum; sound pressure level; sound power; timedelay between signals measured on different body surface locations; andenergy.
 23. The method according to claim 15, wherein said body surfacelocations are selected according to one of predefined options and userdefined locations.
 24. The system according to claim 15, wherein, saidbody surface locations correspond to inner body locations and areselected according to the inner body location for which said audiocharacteristics are to be determined.